410 
man^), James A. Grieg^) and James A. Grieg & H. Friele (l.c. 
1901). {Saxicava rugosa L. is as a synonym reckoned to S. arctica L., 
Thracia villusiuscula Macg. as a variety to 2\ 'papyracea Poli, and 
Buccinopsis ehurnea M. Sars as a variety to B. dalei J. Sowb.). 
As it looks, on tlie whole, as if the species reach greater deptlis 
in the Atlantic, properly so called, tlian off the Norwegian coasts it will 
be seen that there really is not much foundation for the belief that 
most of the dredged species do not live at depths like those from 
which their dead shells have been secured. Yet it is reasonable to 
suppose that fullgrown specimens of Mya truncata hardly would live 
at a deptli of 80 to 100 fms. The depth of 107 fms., mentioned 
by Friele and James A. Grieg, is probably the greatest one 
from which the species has been recorded in a living State. In 
this case, however, there is only a mention of young specimens. 
As I have maintained before (1. c. 1901) it is a general rule that 
young living molluscs caii occur at other depths, both at greater and 
lesser, than the adult specimens^). This may partly be due to 
surface currents, which carry away numerous pelagic larves, and 
’) A. Norman; „A Month on the Trondhjem Fiord“. Ann. & Mag. Nat. 
Hist. 6. S. v. 12. 1893. 
*) James A. Grieg: I. Bidrag til kundskaben om Vestlandets Mol- 
lusker“. Bergens Museums Aarbog. 1896. 
II. „Skrabninger i Vaags^orden og Ulvesund, ytre NordfjoixP. 
Bergens Museums Aarbog. 1897. 
A few illustrating examples to that elfect may be put forth here. The 
greatest depth recorded for living specimens of Cyprina islandica is 
808 fms. (from West of Ireland, „Porcupine“ Exp.). In the British 
Museum, Natural History, I examined, by the kind permission of E. A. 
'Smith, F. Z. S. etc., the specimens dredged at that depth, and I 
found that only one little specimen of about 6 mm. had occurred there 
in a living state, together with a dead specimen of about 4 mm. in 
diameter. The greatest depth from Avhich adult living specimens of 
this species are known in the Atlantic is 50 to 130 fms. — As an 
example of the occurrence of small young ones at le s ser depths than 
the adult specimens may be stated that on the west coast of Iceland 
only young specimens of Modiola modiolus live above the low 
water mark. The adult specimens do not oceur till below the low 
water mark in the Lamenarian-zone. 
